1. Field of the Invention
The invention relates to gas burners and more specifically to gas burners provided with means for reducing NO.sub.x emissions.
2. Description of the Prior Art
The combustion of natural gas in a residential gas furnace normally produces small quantities of various nitrous oxides, generally designated as NO.sub.x compounds. The compounds are undesirable pollutants, and their emission level is being increasingly subjected to regulation by various governmental entities. It has been known for some time that the level of NO.sub.x emission from a gas burner can be reduced by positioning a metallic insert within a certain region of the gas flame produced by the burner. A gas flame typically includes an inner cone having a very high temperature and an outer cone having a somewhat lower temperature. NO.sub.x emissions can be reduced by positioning a metallic insert immediately adjacent the inner cone of the flame. It appears that such inserts function to reduce the temperature of the inner cone, resulting in a decrease in NO.sub.x emissions.
U.S. Pat. No. 4,284,402 discloses the use of a plurality of vanes which are located within a particular region of the flame produced by an oil burner to reduce turbulence, for the purpose of reducing NO.sub.x emissions. This patent discloses, in FIG. 1 and associated text, that it is generally known that a conductive insert can be located adjacent to the inner cone of a flame to control the temperature of that portion of the flame for reducing NO.sub.x emissions.
There are also commercially available multi-port gas burners with NO.sub.x reduction inserts located within the same region of the flame. The inserts comprise steel rod members which are loosely coupled to upstanding supports which are welded to the sides of the burner.